1. Field of the Invention
The invention relates to an improved self-amplifying electromechanical disc brake.
2. Description of the Prior Art
Electromechanical disc brakes are intrinsically known. They are equipped with an electromechanical actuating device that is able to press a friction brake pad against the brake disc in order to actuate the disc brake, i.e. in order to apply the brakes. Usually, the electromechanical actuating device has an electric motor, which, by means of a rotation/translation converting transmission, for example a screw drive, is able to press the friction brake pad against the brake disc. In numerous cases, a reduction gear train is connected between the electric motor and the rotation/translation converting transmission. There are also other possibilities for embodying a rotation/translation converting transmissions; for example, the electric motor, preferably via a reduction gear train, can pivot a cam that presses the friction brake pad against the brake disc or a rack-and-pinion gear can be used in which a gear moves a rack, which moves the friction brake pad. The rack does not necessarily have to be straight.
In order achieve a self-amplification, there are known ramp mechanisms that have one ramp or a set of ramps, which are inclined in relation to the brake disc, i.e. a distance between the ramp(s) and the brake disc decreases in a tangential or circumferential direction of the brake disc. For example, the ramps can be curved in a helical fashion. The slope of the ramp(s) can change over the course of the ramp(s) so that the power of the self-amplification changes during actuation of the disc brake. It is thus possible for the ramp(s) to have a steep slope at the beginning in order to quickly overcome a clearance between the friction brake pad in the brake disc at the beginning of the actuation and for the end(s) of the ramp(s) to have a gradual slope in order to achieve a powerful self-amplification when the actuation force and braking force are high. If the entire length of the ramp(s) has a constant slope, then these are also referred to as a wedge or wedges and as a wedge mechanism. The ramp(s) can be situated on the brake caliper and/or on the friction brake pad, preferably on its rear side oriented away from the brake disc.
The friction brake pad is supported via the ramp(s) against a brake caliper of the disc brake. In order to actuate the disc brake, the electromechanical actuating device slides the friction brake pad along the ramp(s) until the pad rests against the brake disc and presses against the brake disc. The rotating brake disc exerts a friction force on the friction brake pad, acting on it in the direction toward the rising ramp(s). In accordance with the wedge principal, the support of the friction brake pad on the ramp(s) exerts a normal force in relation to the ramps on the friction brake pad, thus exerting a normal force component in relation to the brake disk on the friction brake pad, and presses the friction brake pad against the brake disc in addition to a compressive force exerted by the actuating device. This amplifies the compressive force and braking force of the disc brake.
The known disc brakes have a brake caliper on which or in which the electromechanical parts of the disc brake are accommodated; the expression “electromechanical parts” is understood to include the components of both the actuating device and the self-amplifying device.
The brake caliper of electromechanical disc brakes is usually, but not absolutely, embodied in the form of a floating caliper, i.e. it is able to move in the direction transverse to the brake disc. When the one friction brake pad is pressed against the one side of the brake disc, the brake caliper shifts transversely to the brake disc and presses another friction brake pad against the other side of the brake disc so that only one actuating device and one self-amplifying device are required in order to press both of the friction brake pads into contact. The actuating device and the self-amplifying device do not have to be situated on the same side of the brake disc.